This is a very interesting topic. I've just renewed my EASA medical with my usual AME and we were both surprised - he's known me for a long time - that my CAA record stated my eye colour as blue and hair grey. My eyes are green and I have brown hair. I've only had one medical done by another AME (because I also needed an initial FAA medical at the time); the FAA cert correctly shows both eye and hair colour so I think it unlikely that the second AME entered the new, incorrect data on the CAA system. Very odd. I'm off to my GP on Monday to get a look at what they hold, just in case.